The PPARγ receptors are nuclear receptors (group of approx. 50 transcription factors) which control the expression of many genes that are important for the regulation of lipid metabolism, the synthesis of insulin and the processes of carcinogenesis and inflammation (Bull A W, Arch Pathol Lab Med 2003; 127: 1121-1123) (Koeffler H P, Clin Cancer Res 2003; 9: 1-9) (Youssef J et al., J Biomed Biotec 2004; 3: 156-166).
There are various natural and synthetic agonists which bind to the PPARγ receptors and alter their conformation, giving rise to activation. Natural and synthetic ligands are described in The Lancet 2002; 360:1410-1418.
Recent studies have shown that treatment of tumour cells with ligands of the PPARγ receptors induces a decrease in cellular proliferation, cell differentiation and apoptosis, suggesting potential application of such compounds as agents for preventing carcinogenesis (Osawa E et al., Gastroenterology 2003; 124:361-367).
Other studies have shown that ligands of the PPARγ receptors (e.g. troglitazone) have anti-inflammatory effects and inhibit the mucosal inflammatory response in animal models of IBD (Tanaka T et al., Cancer Res 2001; 61: 2424-2428).
Moreover, evidence has been published very recently that the intestinal anti-inflammatory activity of 5-ASA (5-aminosalicylic acid, mesalazine), the gold standard in the treatment of IBD, is dependent on binding, and consequent activation, of the PPARγ receptors (Rousseaux C et al., J Exp Med 2005; 201: 1205-1215).
The transmembrane receptor with tyrosine-kinase EGF activity is expressed to a very high degree in activated form in various types of neoplasms (Mendelsohn J, Endocr Relat Cancer 2001; 8: 3-9) (Harari P M, Endocr Relat Cancer 2004; 11: 689-708).
Overexpression of the receptor is also related to potential ability of carcinomatous cells to metastasize. In connection to this, it has been demonstrated that EGF promotes the migration and invasiveness of various cell types connected with lesions at the level of interactions with the extracellular matrix (Brunton et al., Oncogene 1997; 14: 283-293).
Numerous studies performed both on experimental animals and in man have established the efficacy of inhibitors of the EGF receptor in controlling proliferation and the spread of tumours (Mendelsohn J, Endocr Relat Cancer 2001; 8: 3-9) (Harari P M, Endocr Relat Cancer 2004; 11: 689-708).
There is no doubt that the intracellular signals triggered by activation of the EGF receptor facilitate the growth and survival of neoplastic cells, contributing to the development of the pathology, and that such signals are essential in determining the ability of tumour cells to spread and colonize remote organs (Mendelsohn J, Endocr Relat Cancer 2001; 8: 3-9) (Kari C et al., Cancer Res 2003; 63: 1-5).
From the foregoing and bearing in mind, moreover, that from the biological standpoint, chronic inflammatory processes play a part in carcinogenesis, it becomes clear that there is a real need for innovative research into new chemical entities which, by their complementary action both on the PPARγ receptors and on the EGF receptors, are able to exert anti-inflammatory and anti-tumour action, of the chemo-preventive, anti-proliferative and anti-metastatic type.